Server log in is rejected

This pc of phil's uses vista x64. It has been successfully on a network and able to log in to the server since it was intoduced into the network.
Recently when a log in to drive L: on the server was tried phil's user name and password were rejected.
The usual error. Incorrect un or pw etc..
Strange thing is the un and pw wil log in on any other pc in the the office.
But go back to phil's and try the same un and pw and it won't log in.
More strange stuff . Internet is ok through the server and all pc's on the network can be seen on phil's but email is not working.
Try to log onto drive L: on the server from phil's and no go. Log onto drive L: from anyother pc in the office and it goes straight in.
I hooked up a laptop to phil's terminal cable and it loged in ok. Put the cable back onto phil's and it wouldn't log in.
So, I am presuming something in phil's pc is blocking the log in but i don't know what and i have everywhere i can thin of.
Any suggestions?
Thanks

 

I'd start by checking that phil is logging in to the domain and not locally to the PC. In vista you can force log in to the domain by entering the user name as domain_name/user_name (it might be a back-slash domain_name\user_name). A local log on would behave the way you describe and explain your symptoms.